Electrolytic manganese dioxide and method for its production, and its application

Abstract

To provide electrolytic manganese dioxide excellent in packing property and high-rate discharge characteristics when used as a cathode material for alkaline dry cells. Electrolytic manganese dioxide in which the half-value width of the (110) plane in XRD measurement using CuKα line as the radiation source is at least 1.8° and less than 2.2°, the peak intensity ratio of X-ray diffraction peaks (110)/(021) is at least 0.70 and at most 1.00, and the JIS-pH (JIS K1467) is at least 1.5 and less than 5.0; a method for producing the electrolytic manganese dioxide; and its application.

Claims

1. Electrolytic manganese dioxide, wherein a half width of the (110) plane in XRD measurement using CuKα line as a light source is at least 1.8° and less than 2.2°, a peak intensity ratio of X-ray diffraction peaks (110)/(021) is at least 0.70 and at most 1.00, and a JIS-pH (JIS K1467) is at least 1.5 and less than 5.0 and wherein, in a volume frequency distribution, with respect to a most frequent particle size (A) and a particle size width (B) at a ½ height of the most frequent particle size (A), the value of (B)/(A) is larger than 1.0 and at most 2.0.

2. The electrolytic manganese dioxide according to claim 1, wherein the half width of the (110) plane in XRD measurement using CuKα line as the light source is at least 2.0° and at most 2.1°.

3. The electrolytic manganese dioxide according to claim 1, wherein the peak intensity ratio of X-ray diffraction peaks (110)/(021) is at least 0.80 and at most 0.90.

4. The electrolytic manganese dioxide according to claim 1, wherein a BET specific surface area is at least 10 m.sup.2/g and at most 40 m.sup.2/g.

5. The electrolytic manganese dioxide according to claim 1, wherein an alkali potential is at least 270 mV and less than 310 mV.

6. A method for producing the electrolytic manganese dioxide as defined in claim 1, wherein an electrolytic current density is at least 0.2 A/dm.sup.2 and less than 0.5 A/dm.sup.2, and a number of days for electrolysis is at least 18 days.

7. The method for producing the electrolytic manganese dioxide according to claim 6, wherein a sulfuric acid-manganese sulfate mixed solution is used whereby a sulfuric acid concentration in an electrolyte at the completion of electrolysis is higher than a sulfuric acid concentration in the electrolyte at initiation of electrolysis, and a sulfuric acid concentration in the electrolyte at completion of electrolysis is at least 32 g/L and at most 55 g/L.

8. A positive electrode active material for a battery, comprising the electrolytic manganese dioxide as defined in claim 1.

9. A battery comprising the positive electrode active material for a battery as defined in claim 8.

10. The electrolytic manganese dioxide of claim 1, wherein the value of (B)/(A) is 1.0 and at most 1.7.

11. The electrolytic manganese dioxide of claim 10, wherein the value of (B)/(A) is 1.1 and at most 1.6.

Description

EXAMPLES

(1) Hereinafter, the present invention will be described in further detail with reference to Examples and Comparative Examples, but the present invention is by no means limited by these Examples.

(2) <Measurement of Alkali Potential of Electrolytic Manganese Dioxide>

(3) The alkali potential of electrolytic manganese dioxide was measured in a 40 wt % KOH aqueous solution as follows.

(4) To 3 g of the electrolytic manganese dioxide, carbon as a conductive agent was added in an amount of 0.9 g to obtain a mixed powder, and 4 ml of a 40 wt % KOH aqueous solution was added to this mixed powder, to obtain a mixture slurry of the electrolytic manganese dioxide, carbon and the aqueous KOH solution. The potential of the mixture slurry was measured, based on the mercury/mercury oxide reference electrodes, to obtain the alkali potential of the electrolytic manganese dioxide.

(5) <Measurement of Press Density of Electrolytic Manganese Dioxide>

(6) For the press density of electrolytic manganese dioxide, electrolytic manganese dioxide having a predetermined weight was put in a ring-shaped mold, and pressed by a piston under a pressure of 1 ton/cm.sup.2 and maintained for 3 seconds. Thereafter, the press-molded pellet of electrolytic manganese dioxide was taken out, whereupon from its height and area, the volume was obtained, and from its weight and volume, the density of the pellet was obtained, and the press density was obtained as its relative value based on the measurement result in Comparative Example 2 being 100%. The higher the press density is represented in the better the packing property.

(7) <Measurement of Half Width (Full Width at Half Maximum: FWHM) by XRD Measurement>

(8) The half width (full width at half maximum: FWHM) of the diffraction line around 22±1° as 28 of the electrolytic manganese dioxide was measured by using an X-ray diffraction apparatus (trade name: MXP-3, manufactured by MAC Science Corporation). The measurement was carried out by using CuKα line (λ=1.5405 Å) as the radiation source, the measurement mode was step scanning, the scanning condition was 0.04° per second, the measuring time was 3 seconds, and the measurement range was within a range of 28 being from 5° to 80°.

(9) <Calculation of (110)/(021) by XRD Measurement>

(10) In an XRD pattern obtained in the same manner as FWHM, the diffraction line=around 22±1° as 2θ was adopted as the peak corresponding to the (110) plane, and the diffraction line around 37±1° as 2θ was adopted as the peak corresponding to the (021) plane. The peak intensity of the (110) plane was divided by the peak intensity of the (021) plane to obtain (110)/(021).

(11) <Measurement of BET Specific Surface Area>

(12) The BET specific surface area of the electrolytic manganese dioxide was measured by nitrogen adsorption by a BET one point method. As the measuring apparatus, a gas adsorption specific surface area measuring apparatus (Flow Sorb III, manufactured by Shimadzu Corporation) was used. Prior to the measurement, the electrolytic manganese dioxide was deaerated by heating at 150° C. for 1 hour.

(13) <JIS-pH of Electrolytic Manganese Dioxide>

(14) The JIS-pH of the electrolytic manganese dioxide was measured by JIS K1467 (ammonium chloride method). That is, a method was employed wherein a certain amount of manganese dioxide was put in a certain amount of an ammonium chloride buffer solution, and the pH of the supernatant was obtained.

(15) <Sulfate Radical and Sodium Contents>

(16) The sulfate radical and sodium contents in the electrolytic manganese dioxide powder particles were measured by dissolving the electrolytic manganese dioxide powder in hydrochloric acid and hydrogen peroxide and measuring the obtained solution by an atomic absorption spectrometry.

(17) <Method for Measuring Particle Size Formulation of Electrolytic Manganese Dioxide>

(18) Measurement of the particle size formulation of electrolytic manganese dioxide was conducted in accordance with the following procedure. 0.03 g of the electrolytic manganese dioxide was put into 20 ml of pure water, and by ultrasonic irradiation, a dispersion slurry was prepared, whereupon measurement of the volume frequency distribution was conducted by a particle size distribution measuring apparatus (MICROTRAC HRA, manufactured by Nikkiso). At that time, in order to measure the accurate amount by dispersing fine particles of at most 1 μm in an aggregated state, it is always necessary to conduct dispersion treatment such as ultrasonic irradiation. If no dispersion treatment is conducted, the fine particles will be measured in a state as aggregated, whereby the amount of the fine particles cannot be accurately measured. Further, at the time of calculating the volume frequency distribution, measurements were conducted at 101 sections to match the 101 channels for measurement set in the particle size distribution measuring apparatus in non-spherical approximation (704.00, 645.60, 592.00, 542.90, 497.80, 456.50, 418.60, 383.90, 352.00, 322.80, 296.00, 271.40, 248.90, 228.20, 209.30, 191.90, 176.00, 161.40, 148.00, 135.70, 124.50, 114.10, 104.70, 95.96, 88.00, 80.70, 74.00, 67.86, 62.23, 57.06, 52.33, 47.98, 44.00, 40.35, 37.00, 33.93, 31.11, 28.53, 26.16, 23.99, 22.00, 20.17, 18.50, 16.96, 15.56, 14.27, 13.08, 12.00, 11.00, 10.09, 9.25, 8.48, 7.78, 7.13, 6.54, 6.00, 5.50, 5.04, 4.63, 4.24, 3.89, 3.57, 3.27, 3.00, 2.75, 2.52, 2.31, 2.12, 1.95, 1.78, 1.64, 1.50, 1.38, 1.26, 1.16, 1.06, 0.97, 0.89, 0.82, 0.75, 0.69, 0.63, 0.58, 0.53, 0.49, 0.45, 0.41, 0.38, 0.34, 0.32, 0.29, 0.27, 0.24, 0.22, 0.20, 0.19, 0.17, 0.16, 0.15, 0.13, 0.12/μm).

(19) <Evaluation of High-Rate Discharge Characteristics>

(20) An aqueous KOH solution was added and mixed into powder mixture comprising 93.7 wt % of electrolytic manganese dioxide and 6.3 wt % of a conductive material, and then the mixture was press-molded to prepare a core of the cathode mixed material. By using this core of the cathode mixed material, a size AA dry cell was prepared, and its high-rate discharge characteristics were evaluated. In the evaluation, the number of pulses in the 1.5 W discharge (ANSI standard discharge) was obtained, and its relative value to the measurement result in Comparative Example 2 being 100%, was obtained.

(21) <Evaluation of Powder Resistance of Electrolyte Manganese Dioxide>

(22) By using the size AA dry cell prepared by the above-mentioned method, the powder resistance of the electrolytic manganese dioxide was evaluated by an AC impedance method. In the evaluation, an AC impedance measuring apparatus (ECI1287A, FRA1255A, manufactured by Toyo Corporation) was used, and the measurement was conducted at a measurement frequency of 120,000 Hz to 0.1 Hz and at an AC voltage ±5 mV. The analysis of measurement data was carried out by the Nyquist plots, and the resistance of the horizontal axis at the time when the imaginary component of the vertical axis of the semi-circular arc component was zero, was calculated, whereupon its relative value, as compared to the measurement result in Comparative Example 1 being 100%, was obtained and adopted as the resistance value of the electrolytic manganese dioxide.

Example 1

(23) Electrolysis was conducted by using an electrolytic bath which has a heating device, and a titanium plate as an anode and a graphite plate as a cathode, which are suspended so as to face each other.

(24) By supplying a manganese sulfate feed solution with a manganese ion concentration of 45 g/L to the electrolytic bath, maintaining the current density to be 0.34 A/dm.sup.2 and the temperature of the electrolytic bath to be 97° C., and adjusting the sulfuric acid concentration at the initial stage of electrolysis and in the second period of electrolysis to be 35 g/L and 52 g/L, electrolysis was conducted for a total of 24 days, i.e. 18 days at the sulfuric acid concentration of the first period and 6 days at the sulfuric acid concentration of the second period.

(25) After the electrolysis, the electrodeposited plate-shaped electrolytic manganese dioxide was washed with pure water and then milled to obtain a milled product of the electrolytic manganese dioxide. Next, this electrolytic manganese dioxide milled product was put in a water bath and stirred, and a 20 wt % sodium hydroxide aqueous solution was added, to conduct a neutralization treatment so as to bring the pH of the slurry to be 2.8. Then, the electrolytic manganese dioxide was washed with water, filtered for separation and dried to obtain an electrolytic manganese dioxide powder. The series of electrolysis conditions are shown in Table 1.

(26) TABLE-US-00001 TABLE 1 Sulfuric acid concentration in Number of days electrolyte for electrolysis Manganese Concentration Number of Total number Current Electrolysis concentration Initial at days after of days for density temperature in the feed concentration termination switching electrolysis Neutralized (A/dm.sup.2) (° C.) solution (g/L) (g/L) (g/L) (days) (days) pH Ex. 1 0.34 97 45 35 52 6 24 2.8 Ex. 2 0.29 97 45 42 — — 28 2.8 Ex. 3 0.37 96 40 38 42 6 24 2.8 Ex. 4 0.34 97 45 35 52 6 24 2.8 Comp. 0.55 96 45 36 — — 15 5.6 Ex. 1 Comp. 0.55 96 45 36 38 4 15 2.5 Ex. 2

(27) The obtained electrolytic manganese dioxide was γ phase. Of the electrolytic manganese dioxide, the half width of (110) was 2.09, the peak intensity ratio of (110)/(021) was 0.8, and the JIS-pH (K1467) was 2.0. These evaluation results are shown in Table 2.

(28) TABLE-US-00002 TABLE 2 Half BET width specific Particle of surface Alkali Sulfate Powder size (110) (110)/ area potential Na radical resistance formulation (deg) (021) JIS-pH (m.sup.2/g) (mV) (ppm) (wt %) (Ω) (B)/(A) Ex. 1 2.09 0.8 2.0 27 296 1100 1.2 84 — Ex. 2 2.03 0.9 2.0 23 270 1050 1.2 — — Ex. 3 2.22 0.9 2.0 27 292 1090 1.2 — 1.02 Ex. 4 2.09 0.8 2.0 27 296 1100 1.2 95 1.04 Comp. 2.8 0.7 3.5 34 286 1160 1.3 — — Ex. 1 Comp. 2.7 0.7 1.9 35 295 324 1.2 100  — Ex. 2

(29) Further, the results of the press density and the high-rate discharge test are shown in Table 3.

(30) TABLE-US-00003 TABLE 3 Press density (%) 1.5 W discharge (%) Ex. 1 102 105 Ex. 2 103 — Ex. 3 103 — Ex. 4 105 107 Comp. 100 — Ex. 1 Comp. 100 100 Ex. 2

Example 2

(31) In the same manner as in Example 1, by adjusting the current density to be 0.29 A/dm.sup.2 and the sulfuric acid concentration to be 42 g/L, electrolysis was conducted for 28 days.

(32) After the electrolysis, the electrodeposited plate-shaped electrolytic manganese dioxide was washed with pure water and then milled to obtain a milled product of the electrolytic manganese dioxide. Next, this electrolytic manganese dioxide milled product was put in a water bath and stirred, and a 20 wt % sodium hydroxide aqueous solution was added, to conduct a neutralization treatment so as to bring the pH of the slurry to be 2.8. Then, the electrolytic manganese dioxide was washed with water, filtered for separation and dried to obtain an electrolytic manganese dioxide powder.

(33) The obtained electrolytic manganese dioxide was γ phase. Of the electrolytic manganese dioxide, the half width of (110) was 2.03, the peak intensity ratio of (110)/(021) was 0.9, and the JIS-pH (K1467) was 2.0. These evaluation results are shown in Table 2.

(34) Further, the result of the press density is in Table 3.

Example 3

(35) In the same manner as in Example 1, by adjusting the manganese ion concentration to be 40 g/L, the current density to be 0.37 A/dm.sup.2, the electrolytic bath temperature to be 96° C., and the sulfuric acid concentrations at the initial stage of electrolysis and in the second period of electrolysis to be 38 g/L and 42 g/L, electrolysis was conducted for a total of 24 days, i.e. 18 days at the sulfuric acid concentration in the first period and 6 days at the sulfuric acid concentration in the second period.

(36) After the electrolysis, the electrodeposited plate-shaped electrolytic manganese dioxide was washed with pure water and then milled by a roller mill (Kurimoto roller mill 42-model, manufactured by Kurimoto, Ltd.) having a 37 kW mill motor and capable of milling a raw material having a hardness of a micro Vickers hardness of 400 HV (JIS Z2244), to obtain a milled product of the electrolytic manganese dioxide. Next, this electrolytic manganese dioxide milled product was put in a water bath and stirred, and a 20 wt % sodium hydroxide aqueous solution was added, to conduct a neutralization treatment so as to bring the pH of the slurry to be 2.8. Then, the electrolytic manganese dioxide was washed with water, filtered for separation and dried to obtain an electrolytic manganese dioxide powder.

(37) The obtained electrolytic manganese dioxide was γ phase. Of this electrolytic manganese dioxide, the half width of (110) was 2.22, the peak intensity ratio of (110)/(021) was 0.9, and the JIS-pH (K1467) was 2.0. These evaluation results are shown in Table 2.

(38) Further, the result of the press density is in Table 3.

Example 4

(39) The electrolytic manganese dioxide obtained by the electrolysis test in Example 1 was further milled by a jet mill (single track jet mill, manufactured by Seishin Enterprise Co., Ltd.) to obtain an electrolytic manganese dioxide powder with a most frequent particle size of 10 μm. This powder and the powder in Example 1 were mixed in proportions of 20 wt % and 80 wt %, respectively, to obtain an electrolytic manganese dioxide powder.

(40) Of the obtained electrolytic manganese dioxide, the most frequent particle size (A) was 48 μm, the particle size width (B) at a ½ height of the most frequent particle size was 50 μm, and the value of (B)/(A) was 1.04. These evaluation results are shown in Table 1.

(41) The obtained electrolytic manganese dioxide was γ phase. Of this electrolytic manganese dioxide, the half width of (110) was 2.09, the peak intensity ratio of (110)/(021) was 0.8, and the JIS-pH (K1467) was 2.0. These evaluation results are shown in Table 2.

(42) Further, the results of the press density and the high-rate discharge test are shown in Table 3.

Comparative Example 1

(43) In the same manner as in Example 1, by adjusting the current density to be 0.55 A/dm.sup.2, the temperature of the electrolytic cell to be 96° C., and the sulfuric acid concentration to be 36 g/L, electrolysis was conducted for 15 days.

(44) After the electrolysis, the electrodeposited plate-shaped electrolytic manganese dioxide was washed with pure water and then milled to obtain a milled product of the electrolytic manganese dioxide. Next, this electrolytic manganese dioxide milled product was put in a water bath and stirred, and a 20 wt % sodium hydroxide aqueous solution was added, to conduct a neutralization treatment so as to bring the pH of the slurry to be 5.6. Then, the electrolytic manganese dioxide was washed with water, filtered for separation and dried to obtain an electrolytic manganese dioxide powder.

(45) The obtained electrolytic manganese dioxide was γ phase. Of the electrolytic manganese dioxide, the half width of (110) was 2.80, the peak intensity ratio of (110)/(021) was 0.7, and the JIS-pH (K1467) was 3.5. These evaluation results are shown in Table 2.

(46) Further, the result of the press density is shown in Table 3.

Comparative Example 2

(47) In the same manner as in Example 1, by adjusting the current density to be 0.55 A/dm.sup.2, the temperature of the electrolytic cell to be 96° C., and the sulfuric acid concentrations at the initial stage of electrolysis and in the second period of electrolysis to be 36 g/L and 38 g/L, electrolysis was conducted for a total of 15 days, i.e. 11 days at the sulfuric acid concentration of the first period, and 4 days at the sulfuric acid concentration of the second period.

(48) After the electrolysis, the electrodeposited plate-shaped electrolytic manganese dioxide was washed with pure water and then milled to obtain a milled product of the electrolytic manganese dioxide. Next, this electrolytic manganese dioxide milled product was put in a water bath and stirred, and a 20 wt % sodium hydroxide aqueous solution was added, to conduct a neutralization treatment so as to bring the pH of the slurry to be 2.5. Then, the electrolytic manganese dioxide was washed with water, filtered for separation and dried to obtain an electrolytic manganese dioxide powder.

(49) The obtained electrolytic manganese dioxide was γ phase. As the physical properties of this electrolytic manganese dioxide, the half width of (110) was 2.70, the peak intensity ratio of (110)/(021) was 0.7, and the JIS-pH (K1467) was 1.9. These evaluation results are shown in Table 2.

(50) Further, the results of the press density and the high-rate discharge test are shown in Table 3.

(51) From Tables 1 to 3, it is evident that by producing electrolytic manganese dioxide at a current density and a total number of days for electrolysis in Examples 1 to 4, it is possible to obtain electrolytic manganese dioxide excellent in crystallinity and JIS-pH as compared to Comparative Examples 1 and 2. Further, it is evident that the electrolytic manganese dioxide in Examples 1 to 4 shows an excellent press density (packing property) and high-rate discharge characteristics as compared to Comparative Examples 1 and 2.

(52) The entire disclosures of Japanese Patent Application No. 2016-66038 filed on Mar. 29, 2016 and Japanese Patent Application No. 2016-213808 filed on Oct. 31, 2016 including specifications, claims, drawings and summaries are incorporated herein by reference in their entireties.

INDUSTRIAL APPLICABILITY

(53) Since the electrolytic manganese dioxide of the present invention has a specific crystal structure, it is useful as a cathode active material for manganese dry cells, in particular alkaline manganese dry cells, excellent in packing property and discharge characteristics, in particular high-rate discharge characteristics.